Generally, a video tape cassette stores a supply reel and a take up reel, both of which perform complementary roles in protecting the tape running between the two reels. In such reels, the lower reel plate and the upper reel plate are coupled conventionally in such a manner that, as shown in FIG. 3, a boss 21 is formed at the centre of a lower reel plate 20, a space 24 having an upward opening is formed outwardly to the boss 21, a cylindrical hub wall 22 is formed uprightly from the face of the lower reel plate 20, and an upper reel plate 23 is mounted upon the boss 21 and the hub wall 22 to be fixed thereon.
In such a structure of the lower reel plate, when a melted resin is injected into a molding die, the resin is press-injected into an injecting section 25 which is formed on the ceiling of the boss 21, and then, the resin is spread into the interior of the injection die. In such a structure, there has been the problem that the resin cannot smoothly flow, and that defects in the form of an overlap 30 occur during the coupling of the upper reel plate.
That is, according to the conventional lower reel plate structure, the resin injected into the injecting section 25 is broken down into the left and right directions in its flowing from the ceiling of the boss, and then, the flowing resin passes along the horizontal bottom of the lower reel plate to finally fill up to the top of the hub wall.
In such a structure, the flowing resin experiences considerable resistances until it is filled up to the top of the hub wall, and consequently, the charging efficiency of the resin is lowered. This brings the result that a time delay is imposed on the press-injecting procedure of the injection molder, thereby reducing the productivity and increasing the power consumption. Further, there occur injection defects which in turn cause product defects, and overlap phenomena occur due to the direct perpendicular crossing of the upper reel plate with the outer face of the hub wall during the coupling of the upper reel plate, with the result that the tape wound on the hub is ultimately damaged.